Currently, climate change (CC) is one of the most serious problems that the world will face in the coming years. The cause of this problem is due to increasing rapidly in the concentration of greenhouse gases (GHGs) in the atmosphere. Carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) are three greenhouse gases produced in the process of agricultural production, the rate of emissions of greenhouse gases in turn were 9% CO2, 45 % CH4, 46% of the conversion of nitrogen and wet-rice cultivation is a major source of gases. In which, N2O is known as a green house gas is 12 times as powerful as CH4 and 296 times as CO2 and it is contributing to potentially damaging to the ozone layer in the last 100 years (IPCC, 2010). Vietnam has 4.1 million hectares of agricultural production is the cultivation of rice (MONRE, 2011), that is why it is necessary to research a science and technology solution to reduce N2O emissions in agriculture sector, more detail on research is a method for managing water properly with good nutrient management for rice to maintain production, while reducing greenhouse gas emissions from rice fields. This paper would also be discussed and shared some of the contents to be done for this research direction.

This paper presents the results of hydrodynamics and morphology in the estuary
and coastal areas of the Mekong Delta. The 1D (MIKE11) and 2D (MIKE21 Coupled FM) models are used to simulate hydrodynamics, sediment transport, and morphological changes in a climate year from May 2009 to April 2010 under current conditions. Analytical results show that the areas are affected by monsoon seasons namely the southwest (from May to October) coinsiding with the rainy season and the northeast (from November to April next year) coinsiding with dry season. During the southwest monsoon, the area of the East Sea experienced dominantly accretion and erosion occured less frequently. The erosion of the area began in the northeast monsoon. This is opposite for the area of West Sea.

This paper presents an approach based on reliability theory for analyzing hydraulic
structure using the reliability index . This approach includes methods of force scheme selection acting on the hydraulic structure and reliability index calculation ranging from simple to complex techniques. Simultaneously, a procedure has been established to define the acceptable reliability and propose suitable reliability values in line with Vietnam situation.

Flood detection and warning methods based on extreme rainfall analysis have
showed some advantages over conventional practices, especially when using regional or global spatial distribution datasets that helps to overcome difficulties in data collection in transboundary river basins. This article introduces a simple approach to assess the risk of flash floods in mountainous areas based on a short duration upstream accumulation precipitation index analyzed using a regional rainfall dataset reconstructed for Asian monsoon areas during period 1961-2007 (APHRODITE). A case study is applied for Ca River Basin and flash flood risks are identified for the entire river network. Results have been preliminarily verified and
reflected a reasonable agreement with the reality and capability for early flood warning.
Key words: Flash flood; extreme upstream accumulation rainfall; APHRODITE rainfall dataset

Climate change causes the extreme weather patterns that lead to flood flows, flood
process curve as well as flood discharge into downstream areas in operation are more different from the initial design in a negative direction that can pose serious risks for the safety of the construction. With a view to forecasting the flow, water level of reservoirs as well as establishing the process curve of flood release into discharge downstream closely to the observed curve that help regulatory agencies responsible for managing dam reservoir as well as local authorities actively respond to the situations when floods occur, this article introduces the application of HEC-HMS software to make forecast for a typical reservoir in the Ba River basin of Dak Lak province as a basis for application to other reservoirs in the region.

The model of rice cultivation on shrimp cultured land, called the Rice-Shrimp
farming model, is considered as a sustainable production model on the Bac Lieu province in particular and Mekong River Delta provinces in general. In this, the freshwater supply for salt washing for rice cultivation is very important, contributing to the productivity and quality of the rice crop. However, the source of freshwater for salt washing of these areas in addition to rainwater, also depends on surface water from the Hau River. In this study, the authors initially assessed the ability to supply freshwater from the Hau River for the production Rice-Shrimp farming region in Bac Lieu province through the simulation of the water resource composition in the present case and after sewers Cai Lon, Cai Be were built case.
Keywords: freshwater source of Hau River, irrigation system, Rice-Shrimp, Bac Lieu.

Vietnam is one of the countries affected the most severely by climate change. Climate change makes increasingly impacts on industries, especially agriculture. In this context, restructuring the agricultural sector is both a solution to boost production, increase economic value, and also adapt to climate change. This paper addresses the impacts of climate change on agriculture in terms of the most elementary and most vulnerable sectors. In addition, this paper summarizes the initial results of the implementation of policy on restructuring the agricultural sector in recent years, and on the other hand, the constraints and causes of the restructuring results in a need of climate adaptation. At the end, the paper proposes recommendations and solutions to promote the process of restructuring the agricultural sector to sustain and adapt to climate change.

The Mekong River in Vietnam has about 250km in length drainages its water
through 9/13 provinces in the Mekong Delta. Recently, riverbank erosion became the most dangerous hazard which had strong influence to livelihood of riparian people. To date, there has been many solutions are assisted for mitigating riverbank erosion, however, due to complexity of issue and high cost of investment, application of those solution is rarely. This paper, author would like to introduce a new lower cost solution but higher efficiency to mitigating riverbank erosion in Tien and Hau River. The application has been applied since 15 yrs ago, and it shows very good application, by using MIKE 3 the author clarify the applicable of permeable groynes
of the Mekong.

Breakwater solution is an active solution to reduce the waves. This is one of the
effective measures to minimize shoreline erosion, especially in the case of soft solutions or passive solutions that are not feasible or low efficiency. This paper presents a summary of the study results with 78 experimental scenarios for different
offshore breakwater configuration with different water level and wave parameters (random waves). The experiment results will serve to define the layout of the offshore breakwaters in accordance with the natural conditions of the each area.

This paper shows some functions to evaluate for undrain shear strength of cohesion
soil when using prefebricated vertical drain combined with pre-surchrage in the world. Base on the analytic theory for the variable values of undrain shear strength, the equation was proposed 0,22 ( ' / ' )0,2 u z s pz vz S  U  S   . This is proposed equation by athours of the paper. In order to check for this modified equation, many physical models and vane shear testing was carried out.
Keywords: undrain shear strength, pre-surchrage.

Flood risk warning at the downstream of reservoirs is now concerned by the
authorities and sectors. To actively respond to and mitigate natural disasters in downstream areas, flood warning is indispensable. This paper presents to the readers the method of combining GIS and hydraulic/hydrological modelling MIKE in establishing flood maps for the downstream of PleiPai reservoir and IaLop spillway.
Keywords: GIS, Flood map, hydraulic modeling, Pleipai Reservoir, IaLop spillway.

The reservoir safety is always a hot and compelling issue that has been high on the
agenda, especially in the context of climate change and degeneration of the buffer layer in the basin that has changed in a negative direction, causing rapid flooding and higher flood peak discharge than the designed capacity; along with the fact that the structures was constructed many years ago, inadequacies in the design and construction process are not suitable for the current requirements, posing serious risks for the safety of the reservoir.. Therefore, when upgrading and repairing the head-works that needs to consider the solutions such as: increasing the crest level of the dam, dam reinforcement or expanding the dimension of spillways to increase drainage capacity. This article introduces some typical solutions to ensure the safety of the head-works Hoa Trung reservoir in case of probable maximum flood PMF as a reference for other reservoirs with similar conditions.

Grid size is one of the most important factors affect to the accuracy of hydraulic
results obtained by mathematical models. Using the 2D-FV hydraulic computation software built by the authors based on the finite volume method to solve 2D nonlinear shallow water equations (2D-NSWE) on a structured grid. The paper estimates influencing of grid size on hydraulic results such as water depth, dischage of flood flow on complex terrain.
Keywords: Grid size, numerical model, 2D-FV model, hydraulic character

Mekong Delta plays a significant important role in the national economy development in Viet Nam, however, due to climate change and the over exploitation of upstream
water resource for economic development, Mekong delta has to face the serious shortage of water, for example drought happened in 2015-2016. In order to ensure water resources safety in Mekong delta, it’s certainly to construct water resource control structures at all river estuary to the sea. That’s new structures which meet the objectives of economic development and ecosystem environment protection.
Keywords: Mekong delta, water resouce recurity, water resouce control.

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ĐÁNH GIÁ CẤP ĐỘ RỦI RO THIÊN TAI DỰA TRÊN THIỆT HẠI

Trung, Le Hai - TLU

Viet Nam is one of the countries most suffering from natural disasters, damage would be of up to 1,5% GDP every year. However, consequences are often determined afterward, during the recovery phase. The paper considers the risk of natural disaster by evaluating the loss in human life and economic. The risk is classified into 5 levels regarding the loss rates counted by GDP and nation population. Together with physical parameters of extreme weather events, these five risk levels would support in warning, responding and recovering from disasters.
Key words: risk; natural disaster; loss of life; economy.

The flow over chute spillway after pillars occur water waves. These waves collide
each other and collide to the side walls of slope, causing the grid of water waves. Using a numerical model, namely 2D-FV to simulate this 3D flow over Taruc spillway – Khanh Hoa casestudy. This result can be validated by a physical model constructed in the Hydraulic Lab of Thuyloi University.
Key words: chute spillway, water wave, numerical model, 2D-FV, 3D flow